Why is the grid set up incorrectly in Sketch APP?

Question

User interface

Please tell me why, when setting up the take.ms/gRelx grid, I want to make the column size 70 and the indents 30, but for some reason if I set 30, then the column size becomes 68, and if I change it to 70, then the indent is 28. It just pisses me off, not I can set up the grid.

Answer 1

Gutter on outside, uncheck